
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <title>复选框（checkbox）全选/全不选/返选</title>
    <style>
        body,dl,dt,dd,p{margin:0;padding:0;}
        body{font-family:Tahoma;font-size:12px;}
        label,input,a{vertical-align:middle;}
        label{padding:0 10px 0 5px;}
        a{color:#09f;text-decoration:none;}
        a:hover{color:red;}
        dl{width:120px;margin:10px auto;padding:10px 5px;border:1px solid #666;border-radius:5px;background:#fafafa;}
        dt{padding-bottom:10px;border-bottom:1px solid #666;}
        dt label{font-weight:700;}
        p{margin-top:10px;}
    </style>
    <script type="text/javascript">
        window.onload = function ()
        {
            var oA = document.getElementsByTagName("a")[0];
            var oInput = document.getElementsByTagName("input");
            var oLabel = document.getElementsByTagName("label")[0];
            var isCheckAll = function ()
            {
                //如果所有的input都被选中的情况下，那个全选按钮也要被选中
                for (var i = 1, n = 0; i < oInput.length; i++)
                {
                    oInput[i].checked && n++
                }
                oInput[0].checked = n == oInput.length - 1;
                oLabel.innerHTML = oInput[0].checked ? "全不选" : "全选"
            };
            //点击第一个input的时候,所有的下面的input都要被选中
            oInput[0].onclick = function ()
            {
                for (var i = 1; i < oInput.length; i++)
                {
                    oInput[i].checked = this.checked
                }
                isCheckAll()
            };
            //其实就是循环取反就可以了
            oA.onclick = function ()
            {
                for (var i = 1; i < oInput.length; i++)
                {
                    oInput[i].checked = !oInput[i].checked
                }
                isCheckAll()
            };
            //实时的检测状态
            for (var i = 1; i < oInput.length; i++)
            {
                oInput[i].onclick = function ()
                {
                    isCheckAll()
                }
            }
        }
    </script>
</head>
<body>
<dl>
    <dt><input type="checkbox" id="checkAll" /><label>全选</label><a href="javascript:;">反选</a></dt>
    <dd>
        <p><input type="checkbox" name="item" /><label>选项（一）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（二）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（三）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（四）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（五）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（六）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（七）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（八）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（九）</label></p>
        <p><input type="checkbox" name="item" /><label>选项（十）</label></p>
    </dd>
</dl>
<center>1、切换全选/全不选文字；2、根据选中个数更新全选框状态；</center>
</body>
</html>
